[xsl] Map functions in XSLT 3.0 static expressions?

I'm having trouble seeing if or how the XSLT 3.0 map functions [1] are
allowed in static expressions [2].
The 'Statically known function signatures' are:
The core functions defined in [Functions and Operators],
together with the functions element-available,
function-available, type-available, and system-property
defined in this specification, plus the set of extension
functions that are present in the static context of
every XPath expression (other than a use-when expression)
within the content of the element that is the parent of
the use-when attribute.
Maps are defined in XSLT 3.0, not in 'Functions and Operators, and
functions defined in the XSLT spec are explicitly not extension functions
[3], so are the map functions allowed in static expressions?
Regards,
Tony Graham tgraham@xxxxxxxxxx
Consultant http://www.mentea.net
Chair, Print and Page Layout Community Group @ W3C XML Guild member
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Mentea XML, XSL-FO and XSLT consulting, training and programming
[1] http://www.w3.org/TR/xslt-30/#map-functions
[2] http://www.w3.org/TR/xslt-30/#static-expression
[3] http://www.w3.org/TR/xslt-30/#dt-extension-function